Novel Chimpanzee Adenovirus-Vectored Respiratory Mucosal Tuberculosis Vaccine: Overcoming Local Anti-Human Adenovirus Immunity for Potent TB Protection
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nature publishing group ARTICLES Novel chimpanzee adenovirus-vectored respiratory mucosal tuberculosis vaccine: overcoming local anti-human adenovirus immunity for potent TB protection M Jeyanathan1,3, N Thanthrige-Don1,3, S Afkhami1,3, R Lai1, D Damjanovic1, A Zganiacz1, X Feng1, X-D Yao1, KL Rosenthal1, M Fe Medina1, J Gauldie1, HC Ertl2 and Z Xing1 Pulmonary tuberculosis (TB) remains to be a major global health problem despite many decades of parenteral use of Bacillus Calmette–Gue´ rin (BCG) vaccine. Developing safe and effective respiratory mucosal TB vaccines represents a unique challenge. Over the past decade or so, the human serotype 5 adenovirus (AdHu5)-based TB vaccine has emerged as one of the most promising candidates based on a plethora of preclinical and early clinical studies. However, anti-AdHu5 immunity widely present in the lung of humans poses a serious gap and limitation to its real-world applications. In this study we have developed a novel chimpanzee adenovirus 68 (AdCh68)-vectored TB vaccine amenable to the respiratory route of vaccination. We have evaluated AdCh68-based TB vaccine for its safety, T-cell immunogenicity, and protective efficacy in relevant animal models of human pulmonary TB with or without parenteral BCG priming. We have also compared AdCh68-based TB vaccine with its AdHu5 counterpart in both naive animals and those with preexisting anti-AdHu5 immunity in the lung. We provide compelling evidence that AdCh68-based TB vaccine is not only safe when delivered to the respiratory tract but, importantly, is also superior to its AdHu5 counterpart in induction of T-cellresponses and immune protection, and limiting lung immunopathology in the presence of preexisting anti-AdHu5 immunity in the lung. Our findings thus suggest AdCh68-based TB vaccine to be an ideal candidate for respiratory mucosal immunization, endorsing its further clinical development in humans. INTRODUCTION after birth in most countries. Although BCG effectively protects Pulmonary tuberculosis (TB) caused by Mycobacterium against disseminated childhood TB, it has failed to effectively tuberculosis (M.tb) has haunted mankind for thousands of control adolescent and adult pulmonary TB.3,5 Thus, there is an years and still remains a top infectious killer.1–4 TB causes B1.4 urgent need to develop novel TB vaccines that can be used for million deaths and 9 million new cases each year. An estimated effective boost vaccination following parenteral BCG priming one-third of the world population is latently infected by M.tb in humans.6 and 5–10% of these people develop active TB some time in their One of the immune evasion strategies that M.tb utilizes is to lives. Despite availability of antibiotics, increased multidrug- significantly slow down the appearance of T-cell immunity in resistant or extensively drug-resistant TB cases continue to pose the lung.7 Such delay or ‘‘immunological gap’’ allows M.tb a a global threat. Bacillus Calmette–Gue´rin (BCG), which has foothold in the lung before immunity is established,7–10 and this been used in humans for many decades, remains the only is likely one of the reasons for the ineffectiveness of parenteral licensed anti-TB vaccine. BCG is given once via the skin shortly BCG vaccination in humans.6,7 Therefore, it is believed that 1McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine and Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada and 2Department of Immunology, The Wistar Institute, Philadelphia, Pennsylvania, USA. Correspondence: Z Xing ([email protected]) 3The first three authors contributed equally to this work. Received 25 September 2014; accepted 20 March 2015; published online 15 April 2015. doi:10.1038/mi.2015.29 MucosalImmunology | VOLUME 8 NUMBER 6 | NOVEMBER 2015 1373 ARTICLES effective boost vaccination strategies ought to fill such a gap in hepatitis C virus.33,35–39 However, up to date, AdCh vector T-cell immunity in the lung.6,7,11,12 Recent preclinical research technology has not been translated to developing TB vaccines. from us and others has identified the respiratory mucosal route Furthermore, its potential for respiratory mucosal application of vaccination to be the most effective way to equip the lung, and the effect of pulmonary anti-AdHu5 immunity on its particularly the surface of the respiratory mucosa (the airway potency are still poorly understood. luminal compartment), with protective T-cell immunity.6,11–14 In this study, for the first time we have applied the new Mucosal vaccination does so via activating mucosal-specialized technology for developing a novel replication-defective AdCh- dendritic cells and upregulating mucosa-homing molecules based TB vaccine for respiratory mucosal application. By using on T cells.10,15,16 Nevertheless, almost all of the TB vaccine preclinical models of human pulmonary TB with or without candidates currently in the TB vaccine pipeline are still being preexisting anti-AdHu5 immunity, we provide compelling developed as parenteral vaccines for human application.4 In evidence that respiratory-mucosally delivered AdCh-based TB this regard, the immune adjuvant used for parenteral delivery of vaccine activates high levels of T-cell responses, provides robust protein-based TB vaccines is unsafe for respiratory mucosal protection, and limits lung pathology at a capacity com- applications.17,18 Replicating mycobacterial-based TB vaccines parable to or even better than its AdHu5 counterpart. are known to cause granulomatous inflammation and cannot Importantly, contrary to AdHu5Ag85A, respiratory mucosal be easily cleared from the lung, thus deemed unsuitable for AdCh68Ag85A-induced protective T-cell immunity is mini- respiratory mucosal vaccination. Recent report on the inability mally affected by anti-AdHu5 immunity preexisting locally in of intradermally delivered MVA (modified vaccinia Ankara)- the lung. Our study supports the AdCh-based TB vaccine to be based TB vaccine to enhance protective immunity in a major an ideal candidate for respiratory mucosal immunization in milestone phase 2b trial19 speaks further to the urgency and the humans and thus warrants its further clinical development. importance of the effort in developing different vaccination strategies such as mucosal vaccination against pulmonary TB. RESULTS However, developing both safe and effective respiratory Molecular construction and characterization of a mucosal-deliverable vaccines represents a unique challenge and chimpanzee adenovirus vector AdCh68-based TB vaccine has recently been identified, at the National Institutes of Health A replication-deficient chimpanzee type 68 adenovirus was (NIH)/Aeras Aerosol TB Vaccine Workshop, to be a new 6,13–15,20 constructed to encode a secreted form of Ag85A, a highly priority. Recombinant, replication-deficient virus-vec- immunogenic secreted antigen of M.tb (AdCh68Ag85A), by tored TB vaccine platforms represent the most attractive 40 12,21–23 using a recently described direct cloning technology (Figure 1a). approach for respiratory mucosal vaccination. Based on Expression of Ag85A is under control of a murine its unrivaled potency, the group C human serotype 5 adenoviral cytomegalovirus promoter and its secretion by mammalian vector system (AdHu5) has been widely used for developing 21,22,24–26 cells is promoted by a human tissue plasminogen signal peptide vaccines against infectious diseases and cancer. sequence (tissue plasminogen activator). All Ag85A genetic Indeed, an AdHu5-based TB vaccine developed by us was expression elements in AdCh68Ag85A are identical to those in robustly protective, particularly when given via the respiratory 41 6,12,21 its human type 5 adenovirus-based TB vaccine AdHu5Ag85A. tract, in a number of animal models. This vaccine has also AdCh68Ag85A was packaged and propagated in 293 cells and recently been evaluated following intramuscular administra- 27 purified under the Good Laboratory Practice conditions. Using tion in a phase 1 clinical study. However, a major gap and a monoclonal antibody specific for Ag85A, the production and limitation to the application of AdHu5-based vaccine to secretion of Ag85A protein were characterized in lung epithelial humans is the pervasive preexisting anti-AdHu5 immunity A549 cells by western immunoblotting. The expected size of resulting from respiratory exposure to AdHu5 virus that not B30 kDa Ag85A protein was detected in both the culture only compromises the potency of the vaccine but may also pose supernatant and cellular lysate from A549 cells infected with a safety concern when given to HIV high-risk popula- 22,24,25,28–32 AdCh68Ag85A but not from those infected with empty vector tions. Although human adenoviruses of rare sero- AdCh68 (Figure 1b). The levels of Ag85A antigen production types such as AdHu35 may circumvent this issue, such vector is by AdCh68Ag85A were found to be comparable to those from poorly immunogenic because of its strong type 1 interferon 33–35 the cells infected with the same dose of AdHu5Ag85A (IFN)-inducing ability. (Figure 1b). These observations form the basis to compare Recently, replication-defective chimpanzee-derived adeno- AdCh68Ag85A with AdHu5Ag85A for their safety, viruses (AdCh) have become an attractive alternative to human immunogenicity, and protective efficacy in vivo. adenoviral counterparts.33,35 Neutralizing antibodies against 29,33–35 AdCh vectors are rarely found in humans. Furthermore, Respiratory mucosal inoculation